Trailers and other vehicles more than 80 inches wide are required by regulation to have side marker, clearance and reflex lamps. In the past, all three of these functions have been incorporated in a single package utilizing only a single light bulb.
The typical side marker, clearance and reflex lamp is frequently exposed to water, moisture or salt spray which can cause corrosion of the electrical contacts and ultimate failure of the lamp. If the lamp is associated with a boat trailer, breakage of the light bulb may occur when the heated bulb is contacted by water during launching of the boat.
In an attempt to overcome the problem of corrosion and possible bulb breakage, boat trailer tail lights have been marketed in which the bulbs are contained within a sealed housing. The seal is accomplished by utilizing a resilient gasket between the lens and the housing. When the light bulb of the sealed tail light burns out and needs replacement, the replacement is normally done by the boat owner. As a result, the sealing gaskets are frequently not properly installed when the lenses are reassembled to the housing, and thus the sealed characteristics are destroyed.
Another approach as used in the past to prevent corrosion and bulb breakage of boat trailer tail lights, has been to design the tail lights on the air entrapment principle as disclosed in U.S. Pat. Nos. 3,106,349 and 3,858,038. With tail lights of this type, the upper end of the housing is sealed, while the lower end of the housing is provided with an opening through which the water can enter. As the water rises in the housing during the launching of the boat, air is entrapped in the upper end of the housing, preventing the water from rising to a level to contact the bulb or the electrical connections. However, constructions such as this are not totally satisfactory, in that water within the housing may be jostled as the trailer is moved over uneven terrain during launching, causing the water to splash against the bulbs and the connections, and moisture and salt spray can enter the housing during transporting.
A more recent attempt to prevent corrosion and bulb breakage in a boat trailer tail light has been to utilize a capsule which contains the bulb, as disclosed in U.S. Pat. No. 4,617,617. In a tail light of this type, the bulb is contained within a transparent capsule, and the lower end of the capsule is provided with a hole through which water can enter the capsule, but due to the closed upper end, the air will be entrapped in the upper end of the capsule to prevent the water from contacting the bulb.